Diabetes is a rapidly expanding, devastating disease that currently affects over 371 million people in the world, with associated healthcare costs exceeding 470 billion dollars in the USA alone. There are two main types of diabetes. Type 1 diabetes affects ˜10% of the patients and is characterized by complete insulinopenia due to autoimmune destruction of the insulin-secreting pancreatic beta cells. Treatment of Type 1 diabetes requires insulin therapy. Type 2 diabetes affects ˜90% of the patients and is a polygenic syndrome with not only a hereditary component but also a strong environmental influence. It is caused by insulin resistance and defective insulin secretion. In most individuals, the pancreatic beta cell compensates for obesity-associated insulin resistance by expanding its functional mass and secretion of insulin. In a subset of ˜20% of obese subjects, beta cell compensation fails and Type 2 diabetes develops. Two major classes of type 2 diabetes drugs are insulin sensitizers (e.g. metformin, thiazolidinediones) and insulin secretagogues (e.g. sulfonylureas, glinides, glucagon-like peptide-1 (GLP-1)-based drugs). Most of the recently approved drugs belong to the latter category and are based on the GLP-1 mechanism, either by pharmacologically enhancing GLP-1 levels (GLP-1 agonists) or by inhibiting the degradation of endogenous GLP-1 (dipeptidyl-peptidase 4 inhibitors). One advantageous feature of these drugs is that they only stimulate insulin secretion when blood glucose levels are elevated (as opposed to sulfonylureas and glinides), thus minimizing the risk of iatrogenic hypoglycemia. A decade ago, the discovery of the G-protein-coupled receptor GPR40 as a fatty acid receptor specifically expressed in beta cells and which stimulates glucose-dependent insulin secretion, sparked interest in the pharmaceutical industry as a potential therapeutic target to enhance insulin secretion in type 2 diabetes, in a manner similar to GLP-1-based drugs. GPR40, also known as free fatty acid receptor 1 (FFAR1), is one of a family of G-protein coupled receptors that, through receptor deorphanization studies, was shown to be endogenously activated by medium- to long-chain saturated and unsaturated fatty acids (˜C12-20) (Brisco, et al., 2003, J. Biol. Chem., vol. 278: pgs 11303-11311; Itoh, et al., 2003, Nature, vol. 422, pgs 173-176; Kotarsky et al., 2003, Biochem. Biophys. Res. Commun., vol. 301, pgs 406-410). In humans and rodents, although present in brain and enteroendocrine cells, its expression is particularly high in pancreatic beta cells and enteroendocrine cells in the gut. Operating primarily through Gαq/11 signaling, GPR40 activation of the beta cell leads to an increase in intracellular calcium levels, which in the presence of glucose, ultimately results in augmented insulin secretion. In enteroendocrine cells, GPR40 activation by fatty acids leads to stimulation of incretin secretion (Edfalk, et al., 2008, Diabetes, vol. 57, pgs 2280-2287). Thus, in addition to directly promoting GSIS from islet beta cells, GPR40 activation in enteroendocrine cells provides an indirect means of stimulating GSIS through the actions of released incretins.
Because of the glucose dependency of GPR40-mediated effects on insulin secretion, selective activation of this receptor provides a unique potential therapeutic mechanism by which to treat the diabetic state with minimal risk of hypoglycemic incidents. Given the relatively restricted tissue expression pattern of GPR40, selective GPR40 receptor agonists may offer the additional advantage of providing an improved safety profile relative to the aforementioned therapeutic agents.
Thus, GPR40 receptor agonists of the present invention may provide a therapeutic benefit for the treatment of diabetes, particularly Type 2 diabetes, as well as diseases, syndromes and disorders, including obesity, obesity-related disorders, impaired glucose tolerance, insulin resistance, metabolic syndrome, other cardiovascular risk factors such as hypertension and cardiovascular risk factors related to unmanaged cholesterol and/or lipid levels, osteoporosis, inflammation, and eczema.